Effects Of Three Dimensional Graphene On The Thermal Conductive And Flame Retardant Properties Of Polyamide 6 Composites

With the development of electronic in high-integrated,high performance,micromation and multifunction,which requires more efficient thermal conduction and dissipation.The polymer-based thermal conductive composites raised concern in the field of thermal dissipation due to their great properties,such as light weight,excellent mechanical properties,good corrosion resistance and easy processing.In this work,we used polyamide 6?PA6?as the polymer matrix,which has excellent mechanical properties and easy processing.Firstly,3 dimensional?3D?graphene foams?GF?were synthesized by self-assemble method.Then PA6 molecular chains were covalent grafting to graphene foam,resulting 3D GF/PA6 composites.We studied the construction of thermal conductive paths,decrease the thermal resistant by in-situ polymerization method and function the 3D graphene to improve the flame retardant performance of the PA6 composite.The main contents and conclusions are as follows:1)Graphene oxide were prepared by oxidized and exfoliated graphite by pressurized oxidation method.Then graphene hydrogel was prepared by hydrothermal method and after pre-freezing and freeze drying 3D graphene foams were obtained.Scanning electron microscopy?SEM?,confocal Raman microscopy?Raman?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FTIR?,X-ray photoelectron spectroscopy,thermal gravimetric analysis?TGA?and other tests were carried out to characterize the structure and morphology of the 3D graphene foam.After reaserch we found that with the hydrothermal process GO sheets were reduced into RGO sheets,breaking the balance of electrostatic force,hydrophilic-hydrophobic force and hydrogen bond,and RGO sheets self-assemble into 3D interconnected graphene foam with the?-?conjugation.Besides,the morphology,porosity and pore size of the GF can be controlled by regulating the time and temperature of the hydrothermal reaction.What's more,the macroscopic morphology of the GF can be controlled macroscopically by selecting different reaction vessels.The PA6 composites were synthesized by in-situ thermal polycondensation method to realize PA6 chains covalently grafted onto the graphene sheets.The 3D interconnected graphene structure favored the formation of the con-secutive thermal conductive paths or networks even at relatively low graphene loadings.As a result,the thermal conductivity was improved by 300%to 0.847 W·m^-1·K^-1 of PA6composites at 2.0 wt%graphene loading from 0.210 W·m^-1·K^-1 of pure PA6 matrix.2)In this paper,the three-dimensional graphene foam was used as the thermal conductive filler and the PA6 composites were synthesized by in-situ thermal polycondensation method to realize PA6 chains covalently grafted onto the graphene sheets through“grafting to”strategy.Overall,the 3D graphene polyamide matrix form an interpenetrating network of two phase system.According to‘‘grafting to”strategy,grafting PA6 chains onto GF would improve the compatibility between GF and PA6 matrix and thus reducing thermal contact resistance.The 3D interconnected graphene structure favored the formation of the consecutive thermal conductive paths or networks even at relatively low graphene loadings.As a result,the thermal conductivity was improved by 300%to 0.847 W·m^-1·K^-1 of PA6 composites at 2.0 wt%graphene loading from 0.210 W·m^-1·K^-1 of pure PA6 matrix.The PGF thermal conductive composites have better thermal conductivity than traditional thermal conductive composites at the same content,and have broad application prospects in thermal interface materials,connectors and other high performance thermal management fields.3)In this paper,the purpose of function 3D graphene was realized by introducing PPAP,which was chosen to act as the surface modifier and functional additive due to its ability to assemble with GO through supermolecular interaction.PPAP and GO formed loose hydrogel through interaction at first.In the process of hydrothermal,PPAP was covalently grafted to GO and GO were reduced into graphene.In the process of hydrothermal reduction PPAP co-assembled with GO to form 3D hybrid foam.After in situ polymerization,PA6 grafted to ZGF hybrid foam to obtain complete PZGF composite.Thanks for its self-supporting 3D network the PZGF composites has anti-dripping effect and due to the introduction of PPAP the PHRR and THR of PZGF composites decrease dramatically,especially for PZGF-3,resulting in the maximum reduction in PHRR 551.8 W/g to 331.3 W/g?40%decrease?and THR 34.5 kJ/g to 24.5 kJ/g?29%decrease?.